From: "Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com>
To: Jeff Law <law@redhat.com>, Joseph Myers <joseph@codesourcery.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: RFC: stack/heap collision vulnerability and mitigation with GCC
Date: Tue, 20 Jun 2017 08:27:00 -0000 [thread overview]
Message-ID: <ebad3e6e-4e92-6f63-747c-ebc07628bcea@arm.com> (raw)
In-Reply-To: <c36f6eb2-2478-c901-9390-bc8492aee09b@redhat.com>
On 19/06/17 20:04, Jeff Law wrote:
> On 06/19/2017 11:50 AM, Joseph Myers wrote:
>> On Mon, 19 Jun 2017, Jeff Law wrote:
>>
>>> A key point to remember is that you can never have an allocation
>>> (potentially using more than one allocation site) which is larger than a
>>> page without probing the page.
>>
>> There's a platform ABI issue here. At least some kernel fixes for these
>> stack issues, as I understand it, increase the size of the stack guard to
>> more than a single page. It would be possible to define the ABI to
>> require such a larger guard for protection and so reduce the number of
>> (non-alloca/VLA-using) functions that need probes generated, depending on
>> whether a goal is to achieve security on kernels without such a fix.
>> (Thinking in terms of how to get to enabling such probes by default.)
> On 32 bit platforms we don't have a lot of address space left, so we
> have to be careful about creating too large of a guard.
>
> On 64 bit platforms we have a lot more freedom and I suspect larger
> guards, mandated by the ABI would be useful, if for no other reason than
> allowing us to allocate more stack without probing. A simple array of
> PATH_MAX characters triggers probing right now. I suspect (but didn't
> bother to confirm) that PATH_MAX array are what causes git to have so
> many large stacks.
>
> Also if we look at something like ppc and aarch64, we've currently got
> the PROBE_INTERVAL set to 4k. But in reality they're using much larger
> page sizes. So we could improve things there as well.
>
There are aarch64 linux systems using 4k pages for compatibility with
existing aarch32 binaries.
R.
>
> jeff
>
next prev parent reply other threads:[~2017-06-20 8:27 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-19 17:07 Jeff Law
2017-06-19 17:29 ` Jakub Jelinek
2017-06-19 17:45 ` Jeff Law
2017-06-19 17:51 ` Jakub Jelinek
2017-06-19 21:51 ` Jeff Law
2017-06-20 8:03 ` Uros Bizjak
2017-06-20 10:18 ` Richard Biener
2017-06-20 11:10 ` Uros Bizjak
2017-06-20 12:13 ` Florian Weimer
2017-06-20 12:17 ` Uros Bizjak
2017-06-20 12:20 ` Uros Bizjak
2017-06-20 12:27 ` Richard Biener
2017-06-20 21:57 ` Jeff Law
2017-06-20 15:59 ` Jeff Law
2017-06-19 18:00 ` Richard Biener
2017-06-19 18:02 ` Richard Biener
2017-06-19 18:15 ` Florian Weimer
2017-06-19 21:57 ` Jeff Law
2017-06-19 22:08 ` Jeff Law
2017-06-20 7:50 ` Eric Botcazou
2017-06-19 17:51 ` Joseph Myers
2017-06-19 17:55 ` Jakub Jelinek
2017-06-19 18:21 ` Florian Weimer
2017-06-19 21:56 ` Joseph Myers
2017-06-19 22:05 ` Jeff Law
2017-06-19 22:10 ` Florian Weimer
2017-06-19 19:05 ` Jeff Law
2017-06-19 19:45 ` Jakub Jelinek
2017-06-19 21:41 ` Jeff Law
2017-06-20 8:27 ` Richard Earnshaw (lists) [this message]
2017-06-20 15:50 ` Jeff Law
2017-06-19 18:12 ` Richard Kenner
2017-06-19 22:05 ` Jeff Law
2017-06-19 22:07 ` Richard Kenner
2017-06-20 8:21 ` Eric Botcazou
2017-06-20 15:50 ` Jeff Law
2017-06-20 19:48 ` Jakub Jelinek
2017-06-20 20:37 ` Eric Botcazou
2017-06-20 20:46 ` Jeff Law
2017-06-20 8:17 ` Eric Botcazou
2017-06-20 21:52 ` Jeff Law
2017-06-20 22:20 ` Eric Botcazou
2017-06-21 17:31 ` Jeff Law
2017-06-21 19:07 ` Florian Weimer
2017-06-21 7:56 ` Andreas Schwab
2017-06-20 9:27 ` Richard Earnshaw (lists)
2017-06-20 21:39 ` Jeff Law
2017-06-21 8:41 ` Richard Earnshaw (lists)
2017-06-21 17:25 ` Jeff Law
2017-06-22 9:53 ` Richard Earnshaw (lists)
2017-06-22 15:30 ` Jeff Law
2017-06-22 16:07 ` Szabolcs Nagy
2017-06-22 16:15 ` Jeff Law
2017-06-28 6:45 ` Florian Weimer
2017-07-13 23:21 ` Jeff Law
2017-07-18 19:54 ` Florian Weimer
2017-06-20 23:22 Wilco Dijkstra
2017-06-21 8:34 ` Richard Earnshaw (lists)
2017-06-21 8:44 ` Andreas Schwab
2017-06-21 8:46 ` Richard Earnshaw (lists)
2017-06-21 8:46 ` Richard Earnshaw (lists)
2017-06-21 9:03 ` Wilco Dijkstra
2017-06-21 17:05 ` Jeff Law
2017-06-21 17:47 ` Wilco Dijkstra
2017-06-22 16:10 ` Jeff Law
2017-06-22 22:57 ` Wilco Dijkstra
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